sftp worked just fine for a while and then all of a sudden for no apparent reason it started giving me problems. i would click the SFTP button, the window would open, no files would display on either side, would say not responding. if i waited long enough the files would show up but it might take 10+ minutes. if i click close on SFTP the whole program was killed/died. This went on for weeks and i just worked around it but i would spend a few mins thinking and looking what might be wrong. i tried all the usual suspects more than once and not help.
tonight i tried it again and same problem happened. i don't know what made me think about it but here's what fixed it.
i do a little of everything, programing, server admin, dish washing, catching chickens, etc

i had my download directory set to a directory that had a ton of files in. not just in size but also in quantity. I created a directory with nothing in it and set it as my download dir. Clicked SFTP and boom all is happy in the SFTP business.
i can only speculate but when SFTP opens it must read the download directory and maybe recursively. When it quit working i must have added that last file it took to break SFTP.
Maybe that helps someone and maybe it don't but i am not charging for the information so don't complain haha